I have issues with a external hard drive

back together and try this.

Try rebooting the computer without any USB devices attached. Then plug in the USB drive, right click on My Computer, select manage, and then click ?Disk Management.? If the drive is not present in the Disk Management window or if you are not able to access it, then the drive may have failed. In this window you should see all of your connected physical drives, their format, if they are healthy, and the drive letter.
Change the drive letter of the drive. Right-click on the drive in the list, and from the resulting menu select "Change Drive Letters and Paths"
Click on Change so you can change the drive letter. Click Change.
Select a new drive letter from the drop down list, preferably the one that is not normally used for this drive. EG: U:
Click Yes on the confirmation screen and you are done.

Click Start and in the Run box type in cmd and press Enter.
At the command prompt type in chkdsk U:/r 'the drive letter that you just added:' EG: U: and press enter.
If it finds any discrepancies it should fix them.

To disable power management on the USB hub:
1. Right-click My Computer, click Properties, click the Hardware tab, and then click Device Manager.
2. Double-click Universal Serial Bus controllers to expand it, right-click USB Root Hub, and then click Properties.
3. Click the Power Management tab.
4. Click to clear the Allow the computer to turn off this device to save power check box, and then click OK.

< modify a bit >

you can use a simple adapter to connect the drive to another computer.

The Coolmax adapter was recently reviewed in TR:

http://tinyurl.com/42vfbl

It is available for $25 from TigerDirect.com:

http://tinyurl.com/4vpu2o

Simply connect the drive to the adapter, and connect the USB cable to a known good computer. The ailing drive will be assigned a drive letter in [i]Explorer[/i]. If the drive is working, simply transfer the files you wish to salvage.

While you're at it, you can scan the sectors using [i]chkdsk.exe[/i] as True Blue has pointed out. If the drive is assigned letter [b]E[/b], type chkdsk E: /F to scan and repair sector errors.

You can also run diagnostic software on the drive (assuming it's working). The Seagate utility is free:

http://tinyurl.com/yvq99t

If the drive checks out OK, you can re-assemble it.

Some usb ports on the computer have different voltages and some are pretty low, so try another usb port and see if the drive in question kicks in.

Please post back if you have any more problems or questions.